Files already allow to specify a default "suggested color".
The syntax for that is (historically....):
0 !CMDLINE -c0
The number after the "-c" is the color number suggested.
For the black 12V motor that would be black (as above).
For the 4.5V motor that would be classic light grey, i.e.
0 !CMDLINE -c7
This is standard LDRAW syntax.
Bricklink just would need to understand/parse that...
The syntax for that is (historically....):
0 !CMDLINE -c0
The number after the "-c" is the color number suggested.
For the black 12V motor that would be black (as above).
For the 4.5V motor that would be classic light grey, i.e.
0 !CMDLINE -c7
This is standard LDRAW syntax.
Bricklink just would need to understand/parse that...